fig3

Figure 3. (A) Equilibrium phase diagram of HfO₂. (B) Regimes showing the free energy difference between the Pca2₁ and Pmn2₁ phases. (C) Possible pathways for the formation of the polar phase^[19]. Reprinted figures with permission from Ref.^[19] Copyright by the American Physical Society. (D) Phase diagram illustrating the relationship between grain radius and temperature for HZO thin films. (E, G, I, K, M) Illustrative schematic figures; (F, H, J, L, N) Corresponding free energy curves^[23]. Figures reprinted with permission from Ref.^[23] Copyright by the Wiley Company.